Conveyor belts are often used to transport containers. A typical conveyor belt is an endless loop that circulates between a drive roller and a deflection roller.
It is often useful to know how fast containers move along the conveyor belt. In principle, this should be a simple problem that depends on the drive speed and the belt's length. However, this is complicated by the fact that the length of the belt changes over time. These changes are either uniform over the belt or local, as a result of variations in material properties or environmental factors.
These changes in belt length that result from elongation lead to malfunctions and the need to carry out preventive maintenance.
Another disadvantage of having the belt change its length arises from a conveyor's interaction with other systems. In many cases, a conveyor feeds containers to other processing machines, all of which assume a particular belt speed. Thus, if the conveyor's belt speed changes, a machine that picks up containers from the container will find itself trying to pick up a container that has not yet arrived.